Here's the article I wrote on survival kits for another site:
There are seven C’s to preparing a survival kit: Combustion, Communication, Consumption, Container, Cordage, Cover, and Cutting. These principles of preparedness apply to any situation from “what do I put in my pockets before I leave the house?” to “what do I stock in my tornado shelter?” In every situation these seven things should be considered. But before we begin to explore each of these, there are two “C’s” you can’t put in a kit. They have to be part of you always.
The two internal “C’s” are Confidence and Conditioning. Confidence is gained through practicing skills and planning. In any situation it’s better to be fit; in a survival situation life may depend on it. One should practice using survival gear. If the item is perishable get two (or three) to have one for practice. Refolding a space blanket is hard but they are cheap so get a few and practice shelters and water collection and even cutting one up to make signals.
Below are the seven “C’s” in a survival kit in alphabetical order. They apply to every day carry (EDC), bug out bags (BOG), get home bags (GHB), remote shelters, and even a home tornado shelter. Each kit should contain multiple methods for each “C.”
Combustion: A lighter, Ferro rod and/or magnesium stick all work with varying degrees of practice. Friction, sun and electrical are other viable means. Again, practice at home on a bright sunny day with a cool drink in hand and comfortable shoes and then again on a rainy winter day and/or night. The kit should contain something to catch a spark such as cotton balls or char cloth. These items have to stay dry to work.
Communication: Communication items include cell phone, whistle, flashlight (with good batteries), flares, and a dye marker if at sea. Every kit should have a signal mirror. As the cost comes down include a personal locating beacon for emergency use.
Consumption: Used to denote the ability to get food. Either the hunter or gatherer method works. The simple bandana can be used for gathering berries, bugs, and snails. Hunting tools include a fishing kit, snare wire, and surgical tubing to make a sling shot, bow, or pole spear. The fishing kit should have braided fishing line, hooks of various sizes, at least one lure, sinkers and a float. Braided fishing line doubles as sewing thread. Natural cork is a good float and cork char makes a good small wound cover against infection. The fishing kit is a convenient place to keep sewing needles.
Container: Used to denote the ability to collect water. The basic container is a cup. Other containers include plastic bags, coated nylon pouches and aluminum foil or a space blanket. These can be used to line a hollowed out area to collect rain. One has to consider whether the container needs to be portable in these instances. The stainless steel water bottle serves several purposes in that it holds allot of water, is portable, and can be used to boil water. In addition to a container, water filtering and treatment are in this category. Water filters are more efficient than boiling and easier to use when on the move. Filters come in all sizes from the straw type for an individual to the reverse osmosis water purification units used in desalinization plants. A good filter will take everything bad out of water including taste. For water treatment, two drops a chlorine bleach will disinfect one quart of clear water.
Cordage: One can never have enough rope. The best and most popular is parachute cord or 550 cord. Always burn the ends when cut to prevent fraying. Also, snare wire can be used as cordage and fishing line is just cordage in the desert. Preserve your cordage by using natural cordage when possible.
Cover: The Mylar space blanket is the go to item for emergency cover. It packs small and light. However, it is flimsy. Because of that, it should be used as a temporary solution until better cover can be found or made. In larger kits, a wool blanket, canvas or plastic tarps and even tents are preferred.
Cutting: Finally we get to what everybody considers the big survival item-the knife. Knives range from the Classic Swiss Army Knife to a single locking blade to a multi-tool to a fixed blade sheath knife to machetes and axes. Creek Stewart’s article for the ArtofManliness is the best I’ve read on knife selection. The kit should include a good sharpener so the cutting blade will remain sharp and safe.
Finally and not a "C," each person should have a separate first aid kit. Mine contains quick clot, 3-4x4 gauze pads, 3” wide roll of gauze, 2” wide roll of gauze, bacitracin and iodine packets, rubber gloves, and a role of medical tape. I also have several Band-Aids and every item is in a waterproof bag. Again, I'm an emergency medical technician and take annual training, your kit should reflect your skills.